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| United States Patent |
5,192,375
|
|
Sawa
, et al.
|
*
March 9, 1993
|
Fe-based soft magnetic alloy
Abstract
An Fe-based soft magnetic alloy essentially consisting of an Fe-based alloy
including fine crystal grains used for such as a magnetic core. An average
size of the fine crystal grains is controlled to 300.ANG. or less. Each of
the fine crystal grains is composed of a body-centered cubic phase at
least partially including a super lattice. This alloy has a high
saturation flux density and excellent soft magnetic characteristics such
as a low iron loss and a high magnetic permeability. This alloy is
suitable as a core material for various kinds of choke coils.
| Inventors:
|
Sawa; Takao (Yokohama, JP);
Okamura; Masami (Yokohama, JP);
Takahashi; Yumiko (Koshigaya, JP)
|
| Assignee:
|
Kabushiki Kaisha Toshiba (Kawasaki, JP)
|
| [*] Notice: |
The portion of the term of this patent subsequent to May 28, 2008
has been disclaimed. |
| Appl. No.:
|
675057 |
| Filed:
|
March 26, 1991 |
Foreign Application Priority Data
| Dec 20, 1988[JP] | 63-319417 |
| Current U.S. Class: |
148/306; 148/302; 148/303; 148/308; 148/310; 148/311; 336/229; 420/83; 420/89 |
| Intern'l Class: |
H01F 001/04 |
| Field of Search: |
148/301,302,303,305,306,307,308,310,311,403,304
420/83,89
336/229
|
References Cited
U.S. Patent Documents
| 4881989 | Nov., 1989 | Yoshizawa et al. | 148/302.
|
| 5019190 | May., 1991 | Sawa et al. | 148/306.
|
Primary Examiner: Sheehan; John P.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
Parent Case Text
The present application is a continuation-in-part of Application Ser. No.
07/661,607, filed on Feb. 28, 1991 now abandoned, which is a divisional of
application Ser. No. 07/454,019, filed Dec. 20, 1989, now U.S. Pat. No.
5,019,190.
Claims
What is claimed is:
1. A toroidal choke coil comprising an Fe-based soft magnetic alloy
essentially consisting of an Fe-based alloy, wherein said Fe-based alloy
includes fine crystal grains having an average size of 300 .ANG. or less
and each of said fine crystal grains is composed of a body-centered cubic
phase at least partially including a super lattice.
2. A choke coil according to claim 1, said Fe-based alloy having the
composition represented by the general formula:
Fe.sub.a Cu.sub.b M.sub.c M'.sub.d M".sub.e Si.sub.f B.sub.g,
wherein M is at least one element selected form the group consisting of Ti,
Zr, Hf, V, Nb, Ta, Cr, Mo, W, and the rare earth elements,
M' is at least one element selected from the group consisting of Ti, Zr,
Hf, V, Nb, Ta, Cr, Mo, W, and the rare earth elements,
M' is at least one element selected from the group consisting of Mn, Al, Ge
and the Platinum elements, and
M" is Co and/or Ni, wherein coefficients of a, b, c, d, e, f and g
respectively satisfy
a+b+c+d+e+f+g=100 (atomic %)
0.01.ltoreq.b.ltoreq.8,
0.01.ltoreq.c.ltoreq.10,
0.ltoreq.d.ltoreq.10,
0.ltoreq.e.ltoreq.20,
10.ltoreq.f.ltoreq.25,
3.ltoreq.g.ltoreq.12 and
17.ltoreq.f+g.ltoreq.3.
3. A choke coil according to claim 1, wherein said choke coil is a common
mode choke coil.
4. A choke coil according to claim 1, wherein said choke coil is a normal
mode choke coil.
5. A toroidal choke coil comprising an Fe-based soft magnetic alloy
essentially consisting of an Fe-based alloy, wherein said Fe-based alloy
includes fine crystal grains having an average size of 300 .ANG. or less
and each of said fine crystal grains is composed of a body-centered cubic
phase at least partially including a super lattice, wherein said toroidal
choke coil is composed of a resin-impregnated magnetic core.
6. A toroidal choke coil comprising an Fe-based soft magnetic alloy
essentially consisting of an Fe-based alloy, wherein said Fe-based alloy
includes fine crystal grains having an average size of 300 .ANG. or less
and each of said fine crystal grains is composed of a body-centered cubic
phase at least partially including a super lattice, wherein said toroidal
choke coil is formed as a dust core.
Description
BACKGROUND OF INVENTION
This invention relates to an Fe-based sort magnetic alloy utilized
particularly suitable for producing such as a magnetic core.
Conventionally, crystalline materials such as Permalloy and Ferrite have
been used as a magnetic core material utilized for such as a switching
regulator operated in a high frequency range.
However, the Permalloy has a low specific resistance, and consequently, the
iron loss thereof increases in a high frequency. On the other hand, the
Ferrite has a low iron loss in a high frequency, but the magnetic flux
density thereof is as low as 5000 Gauss at most, and consequently, the
iron loss thereof increases close to a saturation point when used at a
high operating magnetic flux density.
Recently miniaturization of sizes is desired for a power transformer used
at a switching regulator and for a choke coil, a common mode choke coil
and the like used at a transformer operated in a high frequency.
For the miniaturization, an increase of an operating magnetic flux density
is vital and, in this regard, a decrease of an iron loss of the Ferrite
becomes the key issue for the practical use thereof.
In these days, an amorphous magnetic alloy having no grain (crystalline
particle) has attracted considerable attention as a candidate for
dissolving the above mentioned problems, because the amorphous magnetic
alloy possesses excellent soft magnetic characteristics such as a high
magnetic permeability and a low coercive force and, in this regard, is
sometimes utilized in actual use.
The amorphous magnetic alloy contains Iron (Fe), Cobalt (Co), Nickel (Ni)
as basic components, and Phosphorus (P), Carbon (C), Boron (B), Silicon
(Si), Aluminium (Al), Germanium (Ge) are supplementally added thereto as
elements for achieving amorphous state (Metalloid). However, the amorphous
magnetic alloy does not always shows a low iron loss in every frequency
and low material cost.
For example, an Fe-based amorphous magnetic alloy is economical and
exhibits a very low iron loss almost one-fourth as great as Silicon steel
in a low frequency in the range of 50-60 Hz but, in a high frequency over
the range of 10 KHz, the Fe-based amorphous magnetic alloy shows such a
considerably high iron loss which can hardly be suitable for an equipment
use such as a switching regulator used in a high frequency.
For improving this drawback, a fraction of the Fe of an Fe-based amorphous
magnetic alloy is replaced by a non magnetic metal such as Niobium (Nb),
Molybdenum (Mo) and Chromium (Cr) in order to lower a magneto-striction
for decreasing an iron loss and for increasing a high magnetic
permeability thereof. However, in case of a magnetic core formed by a
resin mold, some compressive stresses are imposed on the magnetic core
because of a curing shrinkage of the resin, so that the inferiority of
magnetic characteristics becomes relatively remarkable as time passing.
For this reason an Fe-based amorphous magnetic alloy has not reached at
sufficient characteristics to suit to the practical use as a soft magnetic
material in a high frequency.
On the other hand, a Co-based amorphous magnetic alloy is put into actual
use as a magnetic parts of electric equipment such as a saturable reactor
because of the low iron loss and the high squareness ratio of magnetic
characteristics thereof in a high frequency. However, the material cost
thereof is comparatively high. As stated above, an Fe-based amorphous
alloy is an economical soft magnetic material but has a restriction in
actual use thereof in a high frequency because of a relatively large
magnetostriction and an inferiority to a Co-based amorphous alloy in
aspect of an iron loss and a magnetic permeability.
Although a Co-based amorphous alloy has superior magnetic characteristics,
the Co-based amorphous alloy has a disadvantage of the high material cost
thereof.
SUMMARY OF THE INVENTION
An object of this invention is to eliminate or improve the defects or
drawbacks encountered to the prior art and to provide an Fe-based soft
magnetic alloy having a high saturation flux density and excellent soft
magnetic characteristics in a high frequency. This and other objects can
be achieved according to this invention by providing an Fe-based soft
magnetic alloy essentially consisting of an Fe-based alloy, characterized
in that the Fe-based alloy includes fine crystal grain having an average
size of 300 .ANG. or less, and each of the fine crystal grains is composed
of a body-centered cubic phase at least partially including a super
lattice.
Thus, the resulting alloy has been found that by limiting the average size
of the crystal grains properly and by existing of a super lattice in the
grains, the alloy can exhibit a excellent magnetic characteristics.
The above objects and features of the present invention will appear more
fully hereinafter from a consideration of the following description taken
in connection with the accompanying drawings and tables.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIGS. 1(a) and 1(b) are graphs showing the x-ray diffraction pattern of the
Fe-based soft magnetic alloy of this invention stated in EMBODIMENT 1 and
an alloy stated in COMPARISON 1 mentioned hereunder, respectively;
FIG. 2 is a graph showing a coercive force and temperature relationship of
the fe-based soft magnetic alloy of this invention stated in EMBODIMENT 2;
FIG. 3 is a graph showing the x-ray diffraction patterns of the fe-based
soft magnetic alloy of this invention stated in EMBODIMENT 2;
FIG. 4 is a graph showing a coercive force and temperature relationship of
the fe-based soft magnetic alloy of this invention stated in EMBODIMENT 3;
and
FIG. 5 is a block diagram of a convential switching power source having
various kinds of choke coils.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In order to achieve the aforesaid object, intensive investigation have been
made by inventors on various kinds of alloys, and as the results of these
investigations, an fe-based magnetic alloy with extremely fine grains
having an average size of 300 .ANG. or less is found to possess
outstanding soft magnetic characteristics and is led to the present
invention, in which the Fe-based magnetic alloy comprises a body-centered
cubic phase containing a super lattice as the crystal structure thereof.
Each unit cell of a body-centered cubis phase (bcc phase) has a structure
such that one atoms is positioned at each corner and at the central
portion of the unit cell.
A preferable composition of the Fe-based magnetic alloy of the present
invention has the composition represented by the general formula of
Fe.sub.a Cu.sub.b M.sub.c M'.sub.d M.sub.e "Si.sub.f B.sub.g, wherein M is
at least one element selected from the group consisting of IVa, Va and VIa
and the rare-earth elements of the periodic table; M' is at least one
element selected from the group consisting of Manganese (Mn), Aluminium
(Al), Germanium (Ge) and elements of the Platinum group; M" is Cobalt (Co)
and/or Nickel (Ni); Fe, Cu, Si and B represent Iron, Copper, Silicon and
Boron respectively.
Each coefficient a, b, c, d, e, f, g respectively satisfy the following
formula:
a+b+c+d+e+f+g=100 (in atomic %)
0.01.ltoreq.b.ltoreq.8
0.01.ltoreq.c.ltoreq.10
0.ltoreq.d.ltoreq.10
0.ltoreq.e.ltoreq.20
10.ltoreq.f.ltoreq.25
3.ltoreq.g.ltoreq.12
17.ltoreq.f+g.ltoreq.30
Mentioned hereunder are the reasons for restricting the kinds of elements
and the average fine grain sizes of this invention.
The explanation starts with the reasons for the element restriction.
Copper (Cu) is effective in order to enhance a corrosion resistance, to
prevent the enlargement of grain sizes and to improve soft magnetic
characteristics such as an iron loss and a magnetic permeability and is
especially effective to prompt an early precipitation of a bcc phase at
the comparably low temperature.
Addition of too little amount of Copper results in no effect on the
reduction of core loss and, to the contrary, exceeding amount thereof
causes deterioration of magnetic characteristics. In this regard, the
content of Copper is restricted in the range of 0.01-8 atomic %, and the
preferred content of Cu in the present invention is 0.1-5, atomic %, in
which range the core loss is particularly small and the permeability is
high.
M is effective not only to uniform grains sizes but also to improve the
soft magnetic characteristics by reducing a magnetostriction and a
magnetic anisotropy and is also effective in order to stabilize magnetic
characteristics against temperature variations. M is especially effective
for stabilizing a bcc phase and can stabilize the bcc phase against larger
ranged temperature variations with a cooperative action of Copper.
Addition of too little amount of M results in no influence and, to the
contrary, exceeding amount thereof causes no non-crystallization and a
reduction of a saturation flux density.
In this regard, the content of M is restricted in the range of 0.01-10
atomic %, and the preferred range is 1-8 atomic %.
In addition to the above effects, each of "M" element selected from the
group consisting of IVa, Va and VIa family elements of the periodic table
has the following effects:
An element selected from the IVa group will spread heat treatment
conditions for obtaining the most suitable magnetic characteristics;
An element selected from the Va group will be effective to improve
toughness and machine workability such as cutting; and
An element from the VIa group will improve wear resistance and roughness of
a material surface.
Among the above mentioned elements, Tantalum (Ta), Niobium (Nb), Tungsten
(W) and Molybdenum (Mo) have considerable effects for improving soft
magnetic characteristics and Vaandium (V) has remarkable effects for
increasing toughness and for improving surface roughness of a material,
and the addition thereof are quite desirable.
M' is an effective element to improve soft magnetic characteristics.
However, addition of excess amount of M' causes the decrease of a
saturation flux density. In this connection, the maximum content of M' is
restricted to maximum 10 atomic %.
Al, which is one of possible elements for M', is effective for generating
fine grains, to improve magnetic characteristics and to stabilize a bcc
phase. Ge is also effective for stabilizing a bcc phase, and an element
selected from the Platinum group, which are another possible elements for
M', will help to improve a corrosion resistance and a wear resistance
respectively.
M" is effective to improve a saturation flux density and successively is
effective to improve a magnetostriction and soft magnetic characteristics.
However, because of the fact that excess amount of M" rather decreases a
saturation flux density, the content thereof is maintained 20 atomic % or
less.
Silicon (Si) and Boron (B) prompt non-crystallization of an alloy can raise
a crystallization temperature and, in consequence, can improve a heat
treatment condition for upgrading magnetic characteristics. Especially, Si
forms solid solution in Fe, which is the main component of fine grains,
and works to reduce a magnetostriction and a magnetic anisotropy. However,
the effectiveness of Si for improving soft magnetic characteristics is not
remarkable when the content of Si is 10 atomic % or less.
When is exceeds 25 atomic %, relatively large coarse grains of micro meters
in diameter are precipitated due to a lack of an ultra rapid quenching
effect.
Si in an essential element to compose a super lattice and the content
thereof is controlled between in the range of 10-25 atomic % for
generating a super lattice and is more preferably controlled in the range
of 10-22 atomic %.
When the content of B is less than 3 atomic %, no sufficient effect on
improving soft magnetic characteristics because of the precipitation of
relatively coarse grains. On the other hand, when it exceeds 12 atomic %,
B element easily precipitates in the course of a heat treatment and
deteriorates soft magnetic characteristics.
The ratio of Si and B satisfying the equation Si/B.gtoreq.1 is desirable to
obtain excellent soft magnetic characteristics.
Especially, by maintaining the amount of Si in the range of 14-20 atomic %,
a magnetostriction .lambda. s comes down to almost zero, and a
deterioration of magnetic characteristics by a resin mold is successfully
prevented and, in addition, superior soft magnetic characteristics
obtained just after a heat treatments can be maintained for a long term.
In this case, the content of M more than 2 atomic % is preferably for
actual use because a corrosion resistance is greatly improved.
An Fe-based soft magnetic alloy according to the present invention can be
obtained by using an aimed fine grain precipitation method. At the aimed
fine grain precipitation method, thin strips of an amorphous alloy
manufactured by liquid quenching method or amorphous powders manufactured
by applying an atomizing or a mechanical alloying method are heat treated
for 10 minutes to 50 hours, preferably for 0.5 hour to 25 hours, at the
temperature range (Tx - 50) to (Tx + 150).degree.C. preferably (Tx - 30)
to (Tx + 120).degree.C. wherein Tx is a crystallization temperature of
aforesaid amorphous alloy when it was measured at a heating rate of 10
deg/min.
Hereunder fine grains of the Fe-based soft magnetic alloy are addressed.
At the Fe-based soft magnetic alloy according to this invention, quite few
fine grains are not preferable because these fine grains yield a too much
amorphous phase and cause a large magnetostriction and depletion of
magnetic characteristics. On the other hand, soft magnetic characteristics
decline when coarse grains with an average size of more than 300 .ANG.
thereof appear.
For these reasons, an average fine grains sizes are maintained 300 .ANG. or
less.
The remaining portion of the base alloy structure other than the fine
crystal grains is may be amorphous.
Hereunder, the method of measuring an average size of fine grains are
explained.
Generally, one crystal grain consists of number of crystallites. However,
in the case of Fe-base alloy having a ultra-fine crystal structure
according to this invention, one crystal grain is deemed as a single
crystal, so that the size of the crystallite is substantially equal to
grain size.
Generally, a size of the crystallite is measured by an X-ray diffraction
method. In this method, as the size of the crystallite becomes, finer, a
width of diffraction pattern varies wider. In this regard, corelation
between the size (D) of the crystallite and the width (W) of the
diffraction pattern is generally given by the following Scherrer's
equation;
##EQU1##
wherein .lambda. is wave length of X-ray, .theta. is Bragg angle, K is
proportional constant respectively.
An average fine grain size according to this invention, will be determined
as arithmetic means of measurement obtained by measuring the same sample
alloy more than 10 times.
An Fe-based soft magnetic alloy of this invention possesses superior soft
magnetic characteristics in a high frequency and can be suitably used as a
high frequency magnetic core material such as for a magnetic head, a thin
film head, a high frequency transformer including high voltage use, a
saturable reactor, a common mode choke coil, a normal mode choke coil, a
high voltage pulse noise filter, a flat inductor, a dust core and a
magnetic switch such as for a laser power source and also can be suitably
sued as a magnetic material or various sensors such as a current sensor, a
directional sensor, a security sensor and a torque sensor.
The present invention will be more clearly understood with reference to the
following embodiments.
EMBODIMENT 1
An amorphous ribbon of an alloy having the composition of Fe.sub.73
Cu.sub.1 Nb.sub.4 Si.sub.15 Br.sub.7, which is 5 mm in width and 14 .mu.m
in thickness, was obtained by a single role method, and a toroidal
magnetic core of 12 mm in inner diameter and 18 mm in outer diameter was
made by winding this thin ribbon.
COMPARISON 1
For a comparison purpose, a toroidal magnetic core having the composition
of Fe.sub.74 Nb.sub.4 Si.sub.15 B.sub.7 was produced by using the same
method as used in the EMBODIMENT 1. Toroidal magnetic cores of the
EMBODIMENT 1 and this COMPARISON 1 ware heat treated for 50 minutes at a
temperature 30.degree. C. above a crystallization temperature of each
magnetic core at a heating rate of 10.degree. C. per one minutes.
The magnetic cores of the EMBODIMENT 1 and this COMPARISON 1 were x-ray
diffraction tested under the conditions that a target was Cu, voltage was
40 kV and electric current was 100 mA.
When x-rays with a specific wave length .lambda. are projected on a surface
of a metal which has ordered super lattices, these x-rays are reflected
from atomic planes in crystals. In other words, according to a x-ray
diffraction method, x-rays are selectively reflected to the specific
directions so as to meet the following the Bragg's equation, wherein
.theta. is an incidence angle, and d is a distance between atomic planes:
n.lambda.=2d sin.theta.(n=1, 2, 3 - - -)
Therefore, the existence of a super lattice can be confirmed by measuring
the amount of reflected x-rays using a x=ray diffraction test. The results
of this x-ray diffraction test are shown in FIGS. 1(a) and (b), wherein a
reflecting rate of x-rays is indicated in count numbers per second (CPS).
In case of the alloy of the EMBODIMENT 1, deflected x-rays peculiar to a
super lattice appear at the vicinity of 2.theta.=27 degrees and 31
degrees, and peaks P.sub.1 and P.sub.2 are confirmed. To the contrary, in
case of the alloy of the COMPARISON 1, no peak of reflected x-rays appears
as shown in FIG. 1(b), and this fact explains no existence of a super
lattice.
As the next step, an initial magnetic permeability .mu.' of 1 KHz (exciting
magnetic fields Hm=5 mOe) and a direct current coercive force Hc were
measured with an impedance analyzer on the magnetic cores made of the
aforesaid two alloys.
In additions, some tests pieces were sampled from each of these magnetic
cores, and the surfaces thereof were observed through a transmission
electron microscope (TEM), and grain sizes thereof were measured. The
obtained data are shown in Table 1.
TABLE 1
__________________________________________________________________________
INITIAL
EXISTENCE
MAGNETIC COERCIVE
CRYSTALLINE
OF SUPER
PERMEABILITY
FORCE PARTICLE
LATTICE .mu.' 1 KHz
Hc(Oe) SIZE (.ANG.)
__________________________________________________________________________
EMBODIMENT 1
OBSERVED
148000 0.006 50-200
COMPARISON 1
NONE 820 0.36 100-300
__________________________________________________________________________
As apparent from the data obtained, an Fe-based soft magnetic alloy of the
present invention possesses excellent magnetic characteristics such as a
high magnetic permeability and a low coercive force.
EMBODIMENT 2
an amorphous ribbon of an alloy having the composition of Fe.sub.73.5
Cu.sub.3.5 Nb.sub.3 Si.sub.14 B.sub.6, which is 10 mm in width and 16
.mu.m in thickness, was prepared by a single inner method, and a toroidal
magnetic core of 12 mm in inner diameter and 15 mm in outer diameter was
formed by winding this thin ribbon.
The toroidal wound core was heat treated for 60 minutes at various
temperatures and coercive forces thereof wee measured. The relationship
between measured coercive forces (Hc) of the toroidal magnetic cores and
heat treatment temperatures are shown in FIG. 2.
As apparent from the FIG. 2, an alloy with a low coercive force can be
obtained in the range of 500.degree.-600.degree. C.
The magnetic core heat treated at 570.degree. C. received a x-ray
diffraction test under the same conditions as the EMBODIMENT 1, and the
test results are indicated in FIG. 3.
As apparent from FIG. 3, the alloy with a low coercive force has reflected
x-rays particular to a super lattice, and peaks P.sub.1 and P.sub.2 were
confirmed. The grain sizes thereof were measured by TEM, and confirmed to
scatter between 100 and 200 .ANG..
EMBODIMENT 3
An amorphous ribbon of an alloy having the composition of Fe.sub.73
Cu.sub.1 Nb.sub.2.5 Si.sub.17 B.sub.6.5 was prepared by a single role
method same as in the EMBODIMENT 1, and a toroidal wound core of 12 mm in
inner diameter, 15 mm in outer diameter and 5 mm in height was formed by
winding this thin ribbon.
The toroidal magnetic cores ware heat treated for 50 minutes at various
temperatures, and a coercive force (Hc) thereof was measured. The
relationship between measured coercive forces of the toroidal magnetic
core and heat treatment temperatures are shown in FIG. 4.
As apparent form the FIG. 4, minimum 6 mOe was obtained at around
510.degree. C.
A x-ray diffraction test on a magnetic core heat treated at around
510.degree. C. among the above mentioned test samples was conducted under
the same conditions as in the EMBODIMENT 1, and reflected x-rays
particular to a super lattice were observed at small deflection angle side
similar to FIG. 1 and FIG. 3. The grain sizes thereof were measured by
TEM, and confirmed to scatter between 100 and 200 .ANG..
EMBODIMENT 4
Amorphous ribbons of various alloys listed in Table 2 were made in the same
manner as in EMBODIMENT 1, and toroidal wound cores of 12 mm in inner
diameter and 15 mm in outer diameter were made by winding these thin
ribbons.
These toroidal wound cores were equally heat treated for 80 minutes at the
same temperature, and an initial magnetic permeability of 1 KHz (exciting
magnetic field Hm=5 mOe) and a d.c. current coercive force on the magnetic
cores thereof were measured with an impedance analyzer as well as the
confirmation of an existence of a super lattice by x-ray diffraction
testes. The obtained data are shown in the same Table 2.
TABLE 2
__________________________________________________________________________
INITIAL
EXISTENCE
COERSIVE
MAGNETIC
SAMPLE OF SUPER
FORCE PERMEABILITY
No. COMPOSITION OF ALLOY
LATTICE Hc(mOe)
.mu.' 1 KHz .times. 10.sup.4
__________________________________________________________________________
1 Fe.sub.73 Cu.sub.1.5 Mo.sub.2.5 Si.sub.16 B.sub.7
OBSERVED
6.5 13.8
2 Fe.sub.71.5 Cu.sub.2 W.sub.2.5 Si.sub.17 B.sub.7
OBSERVED
7.0 13.5
3 Fe.sub.71.5 Cu.sub.2.5 Ta.sub.3 Si.sub.15 B.sub.8
OBSERVED
7.0 13.3
4 Fe.sub.73 Cu.sub.1.5 Sm.sub.2 Si.sub.17 B.sub.6.5
OBSERVED
8.0 13.0
5 Fe.sub.73 Cu.sub.1.5 Nd.sub.2 Si.sub.17 B.sub.6.5
OBSERVED
8.0 13.0
6 Fe.sub.71.5 Cu.sub.1 Mo.sub.3 Ru.sub.3 Si.sub.14.5 B.sub.7
OBSERVED
5.5 14.7
7 Fe.sub.72 Cu.sub.1.5 W.sub.3 Cr.sub.2 Si.sub.15 B.sub.6.5
OBSERVED
6.0 13.9
8 Fe.sub.72 Cu.sub.1 Mo.sub.3 V.sub.2 Si.sub.15.5 B.sub.6.5
OBSERVED
6.0 14.5
9 Fe.sub.72 Cu.sub.1 Mo.sub.3 Mn.sub.2 Si.sub.15.5 B.sub.6.5
OBSERVED
6.0 14.2
10 Fe.sub.69 Co.sub.4 Cu.sub.1.5 Nb.sub.3 Si.sub.15 B.sub.7.5
OBSERVED
6.0 14.1
11 Fe.sub.69 Ni.sub.4 Cu.sub.1.5 Nb.sub.3 Si.sub.15 B.sub.7.5
OBSERVED
6.0 13.9
12 Fe.sub.79 Cu.sub.1 Nb.sub.3 Si.sub.8 B.sub.9
NONE 50 2.0
13 Fe.sub.77 Cu.sub.1 Nb.sub.3 Si.sub.10 B.sub.9
NONE 23 4.8
14 Fe.sub.74 Cu.sub.1 W.sub.3 Si.sub.9 B.sub.13
NONE 20 7.0
__________________________________________________________________________
As apparent from Table 2, samples form the alloy of the present invention
containing a super lattice (sample No. 1 through 11) exhibit superior
magnetic characteristics to those of the samples not containing a super
lattice (sample No. 12 through 14).
The grain sizes thereof were measured by TEM and confirmed to scatter
between 100 and 200 .ANG..
EMBODIMENT 5
Powders of various alloys having composition listed in Table 3 were
prepared by an atomizing method. These powders and round shapes and the
average diameters thereof were ranged 10 to 50 .mu.m.
These powders mixed with liquid glass, which worked as a binder, were
formed into toroidal magnetic coils with the dimensions of 38 mm .times.
19 mm .times. 12.5 mm under pressure, and the sample No. 1 through 6 were
heat treated at the temperature of 540.degree. C. for 60 minutes before
being served as test pieces.
For a comparison purpose, a toroidal magnetic core of sample No. 9 was made
from iron dusts and was prepared in the same manner as the sample No. 1
through 6.
In addition, for a comparison purpose, an evaluation was conducted on a
toroidal magnetic core of sample No. 7 made of Fe.sub.71 Cu.sub.1 Mo.sub.3
Si.sub.13 B.sub.12 amorphous ribbon and No. 8 made of Fe.sub.79 Si.sub.10
B.sub.11 which was formed into the same shape of the sample Nos. 1 to 6,
heat treated, impregnated by resin and gap formed.
Measurements of an initial magnetic permeability .mu.' at 10 KHz and a Q
value (at 100 KHz) representing a loss of magnetism were carried out on
each magnetic core tabulated in Table 3.
TABLE 3
__________________________________________________________________________
INITIAL MAGNETIC
SAMPLE PERMEABILITY
Q VALUE
No. COMPOSITION OF ALLOY
.mu.' 1 KHz 100 KHz
__________________________________________________________________________
1 Fe.sub.72 Cu.sub.4 Ta.sub.3 Si.sub.14 B.sub.7
160 50
2 Fe.sub.72 Cu.sub.4 W.sub.3 Wi.sub.14 B.sub.7
160 50
3 Fe.sub.72 Cu.sub.4 Mo.sub.3 Si.sub.14 B.sub.7
157 48
4 Fe.sub.72 Cu.sub.4 Nb.sub.3 Si.sub.14 B.sub.7
165 53
5 Fe.sub.72 Cu.sub.4 Nb.sub.2 Cr.sub.2 Si.sub.14 B.sub.6
165 52
6 Fe.sub.72 Cu.sub.4 Nb.sub.2 Ru.sub.2 Si.sub.14 B.sub.6
167 55
7 Fe.sub.71 Cu.sub.1 Mo.sub.3 Si.sub.13 B.sub.12
105 28
8 Fe.sub.79 Si.sub.10 B.sub.11 (CUT CORE)
100 25
9 IRON DUST 30 11
__________________________________________________________________________
thus, it has been clarified that all the magnetic cores of the present
invention achieve a high magnetic permeability and a high Q value.
X-ray diffraction tests on magnetic cores, made of the same materials
receiving the same heat treatments, under the same conditions as those of
EMBODIMENT 1 confirmed the fact that reflected x-rays particular to a
super lattice directed to a small deflection angle side. The average grain
sizes thereof were measured by TEM and confirmed to spread between 100 and
200 .ANG..
FIG. 5 shows a block diagram of a conventional switching power source in
which various kinds of choke coils such as a normal mode choke coil, a
common mode choke coil and an output choke coil are provided in order to
control a current flow.
In a case where the power source is for single-phase, three terminals are
provided, i.e., two terminals are for each of the AC liens, one for the
ground. During a switch operation, normal mode noise is liable to be
generated between the two AC lines, while common mode noise is generated
between either one of the AC liens and the ground. The normal choke coil
and the common mode choke coil are used as inductors for the purpose of
reducing the noises of switch operation.
Namely, the normal choke coils are usually formed of powder magnetic core,
and are provided between the two AC lines in order to reduce the normal
mode noise. By the way, the common mode choke coils for reducing a common
mode noise are formed by winding two wires around on a toroidal magnetic
core in reverse mode (anti-phase mode).
On the other hand, output choke coils are commonly formed of resin
impregnated magnetic core, and they are commonly provided in a switching
power source for the purpose of suppressing AC components, thereby to
output a stabilized DC output.
The aforementioned respective choke coil is required to have excellent soft
magnetic characteristics such as a high saturation flux density, a high
magnetic permeability and a low iron loss. In this regard, the Fe-based
soft magnetic alloy according to the present invention has all the desired
characteristics, so it seems to be most suitable to utilize the
outstanding present alloy as a core material.
EMBODIMENT 6
an amorphous thin ribbon of an alloy having the composition of Fe.sub.73
Cu.sub.1 Nb.sub.4 Si.sub.15 B.sub.7, which is 5 mm in width and 14 .mu.m
in thickness, was prepared by utilizing a single roll method. A toroidal
magnetic ore having an outer diameter of 18 mm and an inner diameter of 12
mm was formed by winding the thin ribbon, then the toroidal magnetic core
was heat treated for 50 minutes at a temperature of 550.degree. C. (which
is 30.degree. C. higher than the crystallization temperature of the core
material). A wire was wound around on the core 20 times to form a common
mode choke coil.
COMPARISON 2
For a comparative purpose, a toroidal magnetic core having a composition of
Fe.sub.74 Nb.sub.4 Si.sub.15 B.sub.7 was prepared by using the same method
described in EMBODIMENT 6. The toroidal magnetic core was then heat
treated for 50 minutes at a temperature of 610.degree. C. (which is
30.degree. C. higher than the crystallization temperature of the core
material). In the same manner, a wire was wound around on the core 20
times to form a common mode choke coil.
COMPARISON 3
For a comparative purpose, a common mode choke coil having the same
dimensions and wires as that of EMBODIMENT 6 was prepared by using a
conventional Mn-Zn Ferrite as a core material.
Each of the thus prepared common mode choke coils 1 of EMBODIMENT 6 and
COMPARISONS 2 AND 3 was provided respectively in a switching power source
as shown in FIG. 5, and an effect of noise reduction was measured as a
noise voltage at the time of the power source being operated at a
switching frequency of 40 KHz, 80 KHz and 120 KHz, respectively.
COMPARISON 4
For a comparative purpose, a noise voltage was also measured in a case
where common mode choke was not provided in the switching power source.
The measured values are shown in Table 4 listed hereunder.
TABLE 4
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NOISE VOLTAGE (dB.mu. v)
SWITCHING FREQUENCY
40 KHz 80 KHz 120 KHz
______________________________________
EMBODIMENT 6 60 53 37
COMPARISON 2 75 72 61
COMPARISON 3 70 69 54
COMPARISON 4 77 78 65
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As is clear from Table 4, is confirmed that the common mode choke coil of
EMBODIMENT 6 is effective in reducing the noise of switch operation, in
particular, at high frequency in comparison with the cases of COMPARISONS
2 and 3.
EMBODIMENT 7
An amorphous alloy powder having the composition of Fe.sub.71 Cu.sub.1
Mo.sub.3 Si.sub.13 B.sub.12 was prepared by utilizing an atomizing method.
The alloy powder containing a binder was hot-pressed for 60 minutes at a
temperature of 540.degree. C. to form a magnetic core having an outer
diameter of 38 mm, an inner diameter of 19 mm and a height of 12.5 mm,
then a normal mode choke coil was prepared by using the magnetic core.
COMPARISON 5
For a comparative purpose, a magnetic core was prepared by utilizing a
conventional iron powder as a core material to form a dust core, and a
normal mode choke coil having the same dimensions as that of EMBODIMENT 7
was prepared.
Each of the thus prepared normal mode choke coils 2 of EMBODIMENT 7 and
COMPARISON 5 was provided respectively in the switching power source as
shown in FIG. 5, and a colorific value generated from the choke coil at
the time of switching operation was measured as a temperature rise.
As the result, the temperature rise of the normal choke coil of EMBODIMENT
7 was 5.degree. C., while that of COMPARISON 5 was 20.degree. C.
Accordingly, it is confirmed that the normal choke coil according to the
present invention is proven effective in reducing the noise of switch
operation in comparison with the conventional choke coils.
EMBODIMENT 8
An amorphous alloy having the composition of Fe.sub.78 Cu.sub.1 Nb.sub.2.5
Si.sub.17 B.sub.6.5 was prepared by utilizing a single roll method, and a
toroidal magnetic core having an outer diameter of 15 mm and an inner
diameter of 12 mm was formed. The toroidal magnetic core was heat-treated
for 50 minutes at a temperature of 510.degree. C., then the magnetic core
was resin-impregnated and provided with a gap having a width of 0.2 mm to
form a output choke coil.
COMPARISON 6
For a comparative purpose, an output choke coil was prepared by utilizing
the same manner as expressed in EMBODIMENT 8 except that the heat
treatment was conducted for 50 minutes at the temperature of 400.degree.
C.
Each of the thus prepared output choke coils 3 of EMBODIMENT 8 and
COMPARISON 6 was provided respectively in the switching power source as
shown in FIG. 5, and a temperature rise of the magnetic core was measured
during the switching operation.
As the result, the temperature rise of the output choke coil 3 of
EMBODIMENT 8 was 28.degree. C., while that of COMPARISON 6 was 52.degree.
C. Accordingly, it is confirmed that each of the output choke coils 3
according to the present invention has a small iron loss.
As explained above, the present invention can offer an Fe-base soft
magnetic alloy having excellent soft magnetic characteristics in a high
frequency, as well as a high saturation flux density.
It is to be understood by those skilled in the art that the foregoing
description is preferred embodiments of the disclosed invention and that
various changes and modifications may be made in the invention without
departing from the spirit and scope appended claims.
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